Many of the cell-surface antigens and receptors identified to-date have been classified as members of the immunoglobulin superfamily of proteins (IgSF). IgSF proteins are characterized by one or more disulfide-linked loops formed between a highly conserved and properly spaced pair of cysteine residues, which organizes two beta sheets composed of seven or nine antiparallel beta-strands. These loops, which are referred to as immunoglobulin-like domains, are subclassified as variable or constant immunoglobulin-type domains. The variable, or V-type domains, generally possess disulfide loops with cysteines spaced by 65–75 amino acids and thus accommodate nine antiparallel beta-strands.
By comparison, the constant, or C-type, immunoglobulin domains typically consist of intercysteine distances of 35–55 residues, and thus accommodate only seven antiparallel beta-strands. Although some IgSF members contain multiple domains of a single type (e.g. NCAM with five C2-type domains), most members consist of either a single Ig domain or a mixture of domains of both the V- and C-types (A. F. Williams et al., Annu. Rev. Immunol. 6:381–405, 1988). The IgSF molecules function as receptors for antigen, receptors or counter-receptors for other cell surface molecules including other Ig superfamily molecules and adhesion molecules, and as receptors for cytokines.
Another protein fold motif of this family is the leucine rich repeat (LRR), which is a segment of 20–29 amino acids with a signature pattern of 4 consensus leucines and an asparagine. LRRs most commonly occur in multiple tandem arrays and have been identified in more than 60 different proteins of diverse function (reviewed in B. Kobe and J. Deisenhofer, Trends-Biochem-Sci. 19, 415–21 (1994) and in B. Kobe and J. Deisenhofer, Curr Op in Struct Biol 5, 409–416 (1995)). Examples of this family are found in a range of organisms and include the insulin binding protein acid labile subunit (ALS), the morphogenic protein “18 wheeler,” the neural development protein slit, the receptors for chorionic gonadotropin, lutrophin, and follitrophin, and the transcriptional regulator, CIITA.
The crystal structure of one member of this family, porcine ribonuclease inhibitor (RI), has been determined (B. Kobe and J. Deisenhofer, Nature 366, 751–756 (1993)) and serves as a model for the folding of the LRR regions in other proteins. RI consists entirely of 15 LRRs which assume a beta-strand-turn-helix-turn conformation and assemble into a toroid shaped horseshoe structure. Although diverse in function and cellular localization, a common property of members of the LRR family is protein interaction that, in several instances, has been mapped to the unusual structural region of the LRRs. One indication of the nature of this interaction is revealed by the structure of the complex between RI-and its non-native ligand ribonuclease A (B. Kobe and J. Deisenhofer, Nature 374, 183–186 (1995)). As revealed in both the complexed and uncomplexed structure, the conserved residues of the LRR repeat are buried, serving as foundations for the fold. The specificity for differential protein recognition lies in other non-conserved residues in the repeat.
A second sequence motif often associated with LRRs is a cysteine cluster containing 4 similarly spaced cysteines and a proline residue. These clusters lie immediately N- or C-terminal, or both, to the tandem LRRs, and most frequently occur in proteins associated with adhesion or receptor function. One example of this subfamily is the insulin binding protein acid labile subunit (ALS) (S R Leong et al., Mol Endrocrinol 6, 870–876 (1992)), which forms dimeric complexes with insulin binding proteins (IBP) and trimeric complexes with IBPs and insulin like growth factors (IGFs). These complexes restrict IGFs to the vascular compartment with a long extension of their circulating ½ life, and thereby are critical in the development of endocrine function and in the regulation of glucose homeostasis. A second example is the drosophila protein slit, a secreted protein of glial cells, which is involved in the development of axonal pathways (J M Rothberg et al., Genes Develop. 4, 2169–2187 (1990)).
IgSF Genes in Disease and Therapy
Ig SF proteins have an established, proven history as therapeutic targets. Antigonists or agonists of IgSF proteins have been shown to have many important therapeutic values in preventing, ameliorating or correcting dysfunctions or diseases, including, but not limited to, a cancer such as adenocarcinoma, leukemia, lymphoma, melanoma, myeloma, sarcoma, teratocarcinoma, and, in particular, cancers of the adrenal gland, bladder, bone, bone marrow, brain, breast, cervix, gall bladder, ganglia, gastrointestinal tract, heart, kidney, liver, lung, muscle, ovary, pancreas, parathyroid, penis, prostate, salivary glands, skin, spleen, testis, thymus, thyroid, and uterus; an immune disorder such as acquired immunodeficiency syndrome (AIDS), Addison's disease, adult respiratory distress syndrome, allergies, ankylosing spondylitis, amyloidosis, anemia, asthma, atherosclerosis, autoimmune hemolytic anemia, autoimmune thyroiditis, bronchitis, cholecystitis, contact dermatitis, Crohn's disease, atopic dermatitis, dermatomyositis, diabetes mellitus, emphysema, episodic lymphopenia with lymphocytotoxins, erythroblastosis fetalis, erythema nodosum, atrophic gastritis, glomerulonephritis, Goodpasture's syndrome, gout, Graves' disease, Hashimoto's thyroiditis, hypereosinophilia, irritable bowel syndrome, multiple sclerosis, myasthenia gravis, myocardial or pericardial inflammation, osteoarthritis, osteoporosis, pancreatitis, polymyositis, psoriasis, Reiter's syndrome, rheumatoid arthritis, scleroderma, Sjogren's syndrome, systemic anaphylaxis, systemic lupus erythematosus, systemic sclerosis, thrombocytopenic purpura, ulcerative colitis, uveitis, Werner syndrome, complications of cancer, hemodialysis, and extracorporeal circulation, viral, bacterial, fungal, parasitic, protozoal, and helminthic infections, trauma, X-linked agammaglobinemia of Bruton, common variable immunodeficiency (CVI), DiGeorge's syndrome (thymic hypoplasia), thymic dysplasia, isolated IgA deficiency, severe combined immunodeficiency disease (SCID), immunodeficiency with thrombocytopenia and eczema (Wiskott-Aldrich syndrome), Chediak-Higashi syndrome, chronic granulomatous diseases, hereditary angioneurotic edema, and immunodeficiency associated with Cushing's disease; and a developmental disorder such as renal tubular acidosis, anemia, Cushing's syndrome, achondroplastic dwarfism, Duchenne and Becker muscular dystrophy, epilepsy, gonadal dysgenesis, WAGR syndrome (Wilms' tumor, aniridia, genitourinary abnormalities, and mental retardation), Smith-Magenis syndrome, myelodysplastic syndrome, hereditary mucoepithelial dysplasia, hereditary keratodermas, hereditary neuropathies such as Charcot-Marie-Tooth disease and neurofibromatosis, hypothyroidism, hydrocephalus, seizure disorders such as Syndenham's chorea and cerebral palsy, spina bifida, anencephaly, craniorachischisis, congenital glaucoma, cataract, sensorineural hearing loss, and any disorder associated with cell growth and differentiation, embryogenesis, and morphogenesis involving any tissue, organ, or system of a subject, e.g., the brain, adrenal gland, kidney, skeletal or reproductive system.
Using the above examples, it is clear the availability of a novel cloned immunoglobulin (Ig) superfamily family provides an opportunity for adjunct or replacement therapy, and are useful for the identification of immunoglobulin (Ig) superfamily member agonists, or stimulators (which might stimulate and/or bias immunoglobulin (Ig) superfamily member function), as well as, in the identification of immunoglobulin (Ig) superfamily inhibitors. All of which might be therapeutically useful under different circumstances.
The present invention also relates to recombinant vectors, which include the isolated nucleic acid molecules of the present invention, and to host cells containing the recombinant vectors, as well as to methods of making such vectors and host cells, in addition to their use in the production of BGS-2, BGS-3, BGS-4, and/or BGS-4v1 polypeptides using recombinant techniques. Synthetic methods for producing the polypeptides and polynucleotides of the present invention are provided. Also provided are diagnostic methods for detecting diseases, disorders, and/or conditions related to the BGS-2, BGS-3, BGS-4, and/or BGS-4v1 polypeptides and polynucleotides, and therapeutic methods for treating such diseases, disorders, and/or conditions. The invention further relates to screening methods for identifying binding partners of the polypeptides.